Electrical apparatus



April 1953 E. c. HUTCHINS 2,636,104

ELECTRICAL APPARATUS Filed Sept. 15, 1951 2 SHEETS-SHEET l INVENTOI}. I

April 21, 1953 E, g, U c ms 2,636,104

ELECTRICAL APPARATUS Filed Sept. 15, 1951 2 SHEETS-SHEET 2 1 I I L I l2a 2e I L L W I29 W W y INVEN-ZQR.

Patented Apr. 21, 1953 ELECTRICAL APPARATUS Everett 0. Hutchins, Dayton,Ohio, assignor'to General Motors Corporation, corporation of DelawareDayton, Ohio, a

Application September 15, 1951,SerialNo. 246,829

'7 Claims. 1

This invention relates to electrical apparatus and more particularly toa method'of electrically welding tubing to an extensive metalsurface.

Tubing has been bonded to extensive metal surfaces in many differentways. This has been an expensive manufacturing operation regardless ofthe method used. In the more simple ways, much labor was required.

It is an object of my invention to provide a simple inexpensive methodof bonding tubing to metal surfaces which requires little labor andwhich can be performed rapidly.

It is another object of my invention to use tubing of such a shape andto apply the tubing in such a way to the metal surface that the tubingcan be easily and rapidly electrically Welded to the metal-surface.

According to my invention, I use flat-sided tubing such as square tubingand turn the tubing so that the one corner will contact the metalsurface. V-grooved welding rolls are used to progressively force thecorner of the tubing firmly into contact with the metal surface and atthe same time an electric current is passed from the welding rollthrough the tubing to the metal surface at a sufficient rate to weld thetubing to the metal surface.

Further objects and advantages of the present invention will be apparentfrom the following description, reference being had to the accompanyingdrawings, wherein a preferred form of the present invention is clearlyshown.

In the drawings:

Fig. 1 is a plan view illustrating diagrammatically the welding ofsquare tubing to an extensive metal surface;

Fig. 2 is a fragmentary partly diagrammatic vertical sectional viewshowing the parallel welding of the square tubing to the metal surface;

Fig. 3 is a view in elevation showing a refrigerant evaporating meansformed of the tubing and metal sheet shown in the welding operation inFig. 1; and

Fig. 4 is a fragmentary partly diagrammatic vertical sectional showingthe use of three series welding arrangements for simultaneously weldingsix passes of the square tubing to the metal surface,

Referring now to the drawings and more paricularly to Fig. 1, there isshown an extensive sheet of metal 20 such as sheet steel to which tubingis to be bonded. It has always been a difficult problem to bond tubingto an extensive metal surface. Commonly, copper tubing is soldered byhand methods to the sheet steel. The

copper tubing "is expensive and the soldering methods are likewiseexpensive and not always reliable. It has not been practical toweld-ordinary tubing to sheet steel because the tubing would notwithstand the necessary pressure required to provide a good weld.

To make it possible to weld tubing to the sheet steel 23, I use squaresteel tubing, designated by the reference characters 22, 24, 26, 28, 30and 32, and turn the tubing so one edge of the tubing is presented tothe sheet steel. For the purpose of this particular application, thetubing is first 'bent into serpentine shape and has long straight passes22, 24, 2B, '28,

39 and 32. In the entire serpentine formation, however, the corner 23 ispresented to the sheet steel 26.

The sheet steel 20 with the square tubing in the serpentine formation isthen presented to a multiple roll type welding machine having V- grooves25 in the upper rolls sufliciently deep to receive the upper half of thesquare tubing as best shown in Fig. 2. The tubing has stiff straightsides extending between the grooves 25 and the corner 23. The uppergrooved rolls are designated by the reference characters 34, 36, 38,'40, 42 and 44. These upper rolls are spaced upon the rotatable shaft 46distances equal to the spacing of the straight passes 22, 2d, 26, 28, 30and 32. The sheet 20 is supported by flat-surfaced rolls beneath thegrooved rolls designated by the reference characters 50, 52, and 54which are mounted upon the rotatable shaft 56.

The sheet 20 and the serpentine tubing are first placed so that oneend-of each straight pass of the serpentine tubing is placed beneath thegrooved rolls with the sheet 20 resting upon the lower rolls. Thegrooved rolls are forced together to provide sufficient welding pressurebetween the edge or corner 23 of the square tubing and the adjacentportion of the sheet 20.

The straight sides of the tubing extending between the grooves 25 andthe corner 23 make it possible to apply suilicient welding pressure tothe corner 23 to obtain a good weld. For example, when a 22 gauge sheetis used I prefer to use a welding pressure of about 590 or 600 lbs. butany suitable welding pressure may be used up to the limit of thestrength of the straight sides of the tubing. The corner 23 has an areasufficiently limited in width and yet suiiiciently wide to provide astrong weld with the sheet 20 adequate to provide good heat transferbetween the tubing and the sheetZU.

A welding transformer "58 is shown diagramthat one corner 23 ormatically and its secondary winding has one terminal connected by theconductor 60 to the rotatable shaft 36 and a second terminal connectedby the conductor 62 to the rotatable shaft 56. The transformer 58 issupplied from a suitable alternating current source and provided withsuitable welding controls.

In the manner of roll spot welding and seam welding machines, therollers move the tubing and the sheet 20 as a unit so as toprogressively apply the corner 23 of the tubing to the sheet 20beginning at one end of each of the straight passes and proceeding tothe other end as the welding current is passed from the tubing to thesheet 20 to progressively weld the tubing to the sheet 20 as the tubingand the sheet 20 pass between the upper and lower rolls. The tubing andthe sheet 20 may be cooled continuously by cooling fluid flowing throughor over them.

After the welding operation is completed, the tubing is firmly bonded tothe sheet 25 and the welded structure may then be folded or bent as aunit into any desired shape to form a heat exchange unit. For example,in Fig. 3 the sheet 20 is folded into the form of a rectangle to formside walls of the inner container of a frozen food cabinet or an icecream cabinet. The two ends of the tubing designated by the referencecharacters I54 and I36 are connected to a refrigerant liquefying unit(not shown) to receive liquid refrigerant to provide refrigeration forthe interior of the container. The container so formed is enclosedwithin an insulated cabinet shown in the form of dot-and-dash linesbearing the reference character 68.

Although I prefer to use square tubing since it provides the greaternumber of advantages, it is possible to use other forms of flat-sidedtubing such as triangular tubing and pentagonal tubing. In this case,the upper rolls will be provided with grooves which correspond to theupper portion of the tubing and always apply the tubing so that onecorner of the tubing is presented to the sheet 21] to which it is to bebonded. While I prefer to use steel tubing and steel sheets, it ispossible to use other materials such as aluminum tubing and aluminumsheets.

Although I have shown diagrammatically in Figs. 1 to 3 a simple weldingtransformer arranged to apply welding current in parallel electricalcircuit arrangement to the rolls, if desired, other welding arrangementssuch as multiple welding or series welding arrangements may be used. Forexample, the welding arrangements shown in Fig. 13 on page 379 of theWelding Handbook, Third edition, published by the American WeldingSociety may be used instead of the form shown.

In Fig. 4 is shown one example of multiple series welding forsimultaneously welding the six straight passes of the square tubing withthe corners in contact with the sheet 20 as explained in connection withFigs. 1 to 3. In Fig. 4 three welding transformers I2I, I23 and I25 areconnected in parallel to the supply conductors I21 and I29. Suitablewelding controls, not shown, may be provided. One terminal of thesecondary of the transformer I2! is connected to the V-grooved weldingroll I3I while the second terminal is connected to the V-grooved weldingroll I33. The first two passes of the square tubing are applied to thesheet 20 by these rolls I3I and I33. These rolls I3I and I33, are ofcourse, insulated from each other. Beneath the sheet 20 there isprovided a pair of fiat surfaced rolls I35 and I3! which areelectrically connected. The secondary circuit extends from thetransformer I2I through the roll I3I, the first pass of square tubing,through the sheet 20 to the roll I35, thence to the roll I31, backthrough the sheet 20 and the second pass of square tubing and the rollI33 to the transformer secondary.

In a similar way the secondary of the transformer I23 is connected tothe V-grooved welding roll I39 which applies a third pass of squaretubing to the sheet 20. Beneath the sheet 20 is the flat surfaced rollIdI which is electrically connected to the flat surfaced roll I43,likewise beneath the sheet 20. Above the sheet 20 is the V-groovedwelding roll I45 which applies a fourth pass of square tubing to thesheet 20. It is electrically connected to the second terminal of thesecondary of the transformer I23 to complete the welding circuit.

One terminal of the secondary of the transformer I25 is connected to theV-grooved welding roll I47 which applies the fifth pass of square tubingto the sheet 28. Beneath the sheet 20 there is provided a fiat surfacedroll I49 which is electrically connected to the flat surfaced roll I5l,likewise beneath the sheet 25. Above the roll I5I there is provided asixth V-grooved welding roll I53 for applying the sixth pass of tubingto the sheet 26. It is insulated from the roll I l? and is electricallyconnected to the second terminal of the secondary of the weldingtransformer I25.

Thus, in this arrangement the three welding transformers I2I, 123, andI25 each have their secondaries connected to a series welding circuitwhich includes the two separated insulated V-grooved welding rolls andtwo electrically connected fiat surfaced welding rolls beneath the sheet28. This arrangement insures substantially even current flow as thepasses of square tubing are progressively rolled and welded as the sheet25 and the six passes of square tubing are passed progressively from oneend to the other between the rolls.

While the form of embodiment of the invention as herein disclosedconstitutes a preferred form, it is to be understood that other formsmight be adopted, as may come within the scope of the claims Whichfollow.

What is claimed is as follows:

1. The method of bonding fiat sided tubing to an extensive metal surfacewhich includes forcing one of the corners of the tubing into firmcontact with the metal surface and while the tubing is so held passingan electric current at a sufficient rate for a sufficient time throughthe point of contact to weld said one corner to the metal surface.

2. The method of bonding flat sided tubing to an extensive metal surfacewhich includes progressively forcing one of the corners edges of thetubing into firm contact with the metal surface and passing an electriccurrent at a sufficient rate at the progressively moving point ofcontact to progressively weld the one edge of the tubing to the metalsurface.

3. The method of bonding fiat sided tubing to an extensive metal surfacewhich includes progressively applying force to all except two ad- Itensive metal surface, and passing an electric 7 current at a sufiicientrate through the progressively moving point of contact of said edge withthe extensive surface to progressively weld the edge to the extensivesurface.

4. The method of welding flat sided tubing to the surface of anextensive metal member which includes progressively rolling the tubingwith an edge in contact with said surface and passing an electriccurrent between the point of rolling and the metal member at asufficient rate to weld said edge progressively to said surface of saidmember.

5. The method of bonding fiat sided tubing to an extensive metal surfacewhich includes forming the tubing into a serpentine shape with longstraight .passes and with one of the corners of the tubing continuouslyprojecting into contact with the hypothetical plane which would contactone side of the serpentine shaped tubing, placing the serpentine shapedtubing upon the extensive metal surface with said one corner contactingthe metal surface, progressively forcing said one corner of the tubinginto contact with the metal surface and passing an electric current at asuilicient rate between the tubing and the metal surface adjacent to andas said one corner is being progressively forced into contact with saidmetal surface to electrically weld the tubing to the metal surface.

6. The method of bonding flat sided tubing to an extensive metal surfacewhich includes forming the tubing into a serpentine shape with longstraight passes and with one of the corners of the tubing continuouslyprojecting into contact with the hypothetical plane which would contactone side of the serpentine shaped tubing, placing the serpentine shapedtubing upon the extensive metal surface with said one corner contactingthe metal surface, progressively forcing said one corner of each of saidlong straight passes simultaneously into contact with the metal surfaceand passing an electric current at a sufficient rate between the tubingand the metal surface at each point of progressive forcing of the cornerinto contact with the metal surface to simultaneously progressivelyelectrically weld the long straight passes of the tubing to the metalsurface.

7. The method of bonding flat sided tubing to an extensive metal surfacewhich includes forming the tubing into a serpentine shape with longstraight passes and with one of the corners of the tubing continuouslyprojecting into contact with the hypothetical plane which would contactone side of the serpentine shaped tubing, placing the serpentine shapedtubing upon the extensive metal surface with said one corner contactingthe metal surface, progressively applying force to all except the twosides adjacent said corner of the tubing in such a direction as to forcesaid one corner of each of said long straight passes simultaneously intocontact with the metal surface and passing an electric current at asuincient rate between the tubing and the metal surface at each point ofprogressive forcing of the corner into contact with the metal surface tosimultaneously progressively electrically weld the long straight passesof the tubing to the metal surface.

EVERETT C. HUTCHINS.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 1,228,789 Lachman June 5, 1917 2,127,685 Greulich Aug. 23,1938 2,306,772 Benson Dec. 29, 1942 2,333,600 Tra'utvetter Nov. 2, 19432,359,926 McCullough et a1. Oct. 10, 194;

